diff --git a/include/llvm/PassRegistry.h b/include/llvm/PassRegistry.h
index 8c1be67069f..1fb11ed64c1 100644
--- a/include/llvm/PassRegistry.h
+++ b/include/llvm/PassRegistry.h
@@ -36,20 +36,43 @@ class PassRegistry {
   void *getImpl() const;
    
 public:
+  /// getPassRegistry - Access the global registry object, which is 
+  /// automatically initialized at application launch and destroyed by
+  /// llvm_shutdown.
   static PassRegistry *getPassRegistry();
   
+  /// getPassInfo - Look up a pass' corresponding PassInfo, indexed by the pass'
+  /// type identifier (&MyPass::ID).
   const PassInfo *getPassInfo(const void *TI) const;
+  
+  /// getPassInfo - Look up a pass' corresponding PassInfo, indexed by the pass'
+  /// argument string.
   const PassInfo *getPassInfo(StringRef Arg) const;
   
+  /// registerPass - Register a pass (by means of its PassInfo) with the 
+  /// registry.  Required in order to use the pass with a PassManager.
   void registerPass(const PassInfo &PI);
+  
+  /// registerPass - Unregister a pass (by means of its PassInfo) with the 
+  /// registry.
   void unregisterPass(const PassInfo &PI);
   
-  /// Analysis Group Mechanisms.
+  /// registerAnalysisGroup - Register an analysis group (or a pass implementing
+  // an analysis group) with the registry.  Like registerPass, this is required 
+  // in order for a PassManager to be able to use this group/pass.
   void registerAnalysisGroup(const void *InterfaceID, const void *PassID,
                              PassInfo& Registeree, bool isDefault);
   
+  /// enumerateWith - Enumerate the registered passes, calling the provided
+  /// PassRegistrationListener's passEnumerate() callback on each of them.
   void enumerateWith(PassRegistrationListener *L);
+  
+  /// addRegistrationListener - Register the given PassRegistrationListener
+  /// to receive passRegistered() callbacks whenever a new pass is registered.
   void addRegistrationListener(PassRegistrationListener *L);
+  
+  /// removeRegistrationListener - Unregister a PassRegistrationListener so that
+  /// it no longer receives passRegistered() callbacks.
   void removeRegistrationListener(PassRegistrationListener *L);
 };